/**
 * Sudoku Game - Professional Styles
 * Version: 2.0.0
 * Responsive, accessible, modern design
 */

:root {
  --primary: #2196f3;
  --primary-dark: #1976d2;
  --secondary: #ff9800;
  --success: #4caf50;
  --error: #f44336;
  --warning: #ffc107;

  --gray-50: #fafafa;
  --gray-100: #f5f5f5;
  --gray-200: #eeeeee;
  --gray-300: #e0e0e0;
  --gray-700: #616161;
  --gray-900: #212121;

  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;

  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 16px;

  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 8px rgba(0, 0, 0, 0.15);
  --shadow-lg: 0 8px 16px rgba(0, 0, 0, 0.2);
}

/* Reset */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  color: var(--gray-900);
  line-height: 1.6;
}

/* Screens */
.screen {
  min-height: 100vh;
  padding: var(--spacing-lg);
  display: flex;
  align-items: center;
  justify-content: center;
}

.screen.hidden {
  display: none;
}

.container {
  max-width: 900px;
  width: 100%;
  background: white;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  padding: var(--spacing-lg);
}

/* Header */
.game-header {
  text-align: center;
  margin-bottom: var(--spacing-lg);
  padding-bottom: var(--spacing-md);
  border-bottom: 2px solid var(--gray-200);
}

h1 {
  font-size: clamp(2rem, 5vw, 3rem);
  color: var(--primary);
  margin-bottom: var(--spacing-sm);
}

.subtitle {
  color: var(--gray-700);
  font-size: 1.1rem;
}

.game-info-bar {
  display: flex;
  justify-content: space-around;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  margin-top: var(--spacing-md);
}

.info-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.25rem;
}

.info-label {
  font-size: 0.9rem;
  color: var(--gray-700);
}

.info-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary);
}

/* Difficulty Selection */
.difficulty-section {
  margin-bottom: var(--spacing-lg);
}

h2 {
  text-align: center;
  margin-bottom: var(--spacing-md);
  color: var(--gray-900);
}

.difficulty-buttons {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--spacing-md);
}

.difficulty-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-lg);
  background: var(--gray-50);
  border: 3px solid var(--gray-300);
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all 0.25s;
}

.difficulty-btn:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: var(--primary);
}

.difficulty-icon {
  font-size: 3rem;
}

.difficulty-label {
  font-size: 1.2rem;
  font-weight: 700;
}

.difficulty-desc {
  font-size: 0.9rem;
  color: var(--gray-700);
  text-align: center;
}

/* Sudoku Grid */
.sudoku-grid {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: 1px;
  background: var(--gray-900);
  border: 3px solid var(--gray-900);
  width: min(500px, 100%);
  margin: 0 auto var(--spacing-lg);
  aspect-ratio: 1;
}

.sudoku-cell {
  background: white;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(1.2rem, 3vw, 2rem);
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
  user-select: none;
}

.sudoku-cell:hover {
  background: var(--gray-100);
}

.sudoku-cell.initial {
  background: var(--gray-200);
  color: var(--gray-900);
  font-weight: 700;
  cursor: not-allowed;
}

.sudoku-cell.user-filled {
  color: var(--primary);
}

.sudoku-cell.hint-filled {
  color: var(--secondary);
}

.sudoku-cell.selected {
  background: #e3f2fd !important;
  outline: 3px solid var(--primary);
  z-index: 1;
}

.sudoku-cell.highlighted {
  background: #f5f5f5;
}

.sudoku-cell.box-right {
  border-right: 3px solid var(--gray-900);
}

.sudoku-cell.box-bottom {
  border-bottom: 3px solid var(--gray-900);
}

.sudoku-cell.correct-animation {
  animation: correctPulse 0.5s;
}

.sudoku-cell.incorrect-animation {
  animation: incorrectShake 0.5s;
}

/* Number Pad */
.number-pad {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: var(--spacing-sm);
  max-width: 500px;
  margin: 0 auto var(--spacing-lg);
}

.number-btn {
  aspect-ratio: 1;
  background: var(--gray-100);
  border: 2px solid var(--gray-300);
  border-radius: var(--radius-md);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--gray-900);
  cursor: pointer;
  transition: all 0.2s;
}

.number-btn:hover {
  background: var(--primary);
  color: white;
  transform: scale(1.05);
}

.number-btn:active {
  transform: scale(0.95);
}

/* Action Buttons */
.action-buttons {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-lg);
}

.btn {
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all 0.2s;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.btn:active {
  transform: translateY(0);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-hint {
  background: var(--warning);
  color: var(--gray-900);
}

.btn-undo,
.btn-redo {
  background: var(--gray-300);
  color: var(--gray-900);
}

.btn-notes {
  background: var(--gray-300);
  color: var(--gray-900);
}

.btn-notes.active {
  background: var(--primary);
  color: white;
}

.btn-clear {
  background: var(--error);
  color: white;
}

.btn-reset {
  background: var(--gray-500);
  color: white;
}

.btn-new {
  background: var(--primary);
  color: white;
}

.btn-primary {
  background: var(--primary);
  color: white;
}

.btn-large {
  padding: var(--spacing-md) var(--spacing-lg);
  font-size: 1.2rem;
}

/* Feedback */
.feedback {
  text-align: center;
  padding: var(--spacing-md);
  border-radius: var(--radius-md);
  font-weight: 600;
  margin-bottom: var(--spacing-md);
  animation: slideDown 0.3s;
}

.feedback.hidden {
  display: none;
}

.feedback.error {
  background: var(--error);
  color: white;
}

.feedback.info {
  background: var(--primary);
  color: white;
}

/* Results Screen */
.results-header h1 {
  margin-bottom: var(--spacing-md);
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
}

.stat-card {
  background: var(--gray-50);
  padding: var(--spacing-lg);
  border-radius: var(--radius-lg);
  text-align: center;
  box-shadow: var(--shadow-sm);
}

.stat-card .stat-icon {
  font-size: 2rem;
  display: block;
  margin-bottom: var(--spacing-xs);
}

.stat-card .stat-label {
  display: block;
  font-size: 0.9rem;
  color: var(--gray-700);
  margin-bottom: var(--spacing-xs);
}

.stat-card .stat-value {
  display: block;
  font-size: 2rem;
  font-weight: 700;
  color: var(--primary);
}

.badges-container {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
}

.badge {
  background: linear-gradient(135deg, #ffd700 0%, #ffa500 100%);
  padding: var(--spacing-md);
  border-radius: var(--radius-lg);
  text-align: center;
  min-width: 100px;
  animation: badgeAppear 0.5s;
}

.badge-icon {
  font-size: 2.5rem;
  display: block;
  margin-bottom: var(--spacing-xs);
}

.badge-name {
  font-weight: 700;
  color: var(--gray-900);
}

.no-badges {
  text-align: center;
  color: var(--gray-700);
  font-style: italic;
}

.skills-container {
  margin-bottom: var(--spacing-lg);
}

.skill-item {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-md);
}

.skill-name {
  min-width: 150px;
  font-weight: 600;
}

.skill-bar {
  flex: 1;
  height: 20px;
  background: var(--gray-200);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.skill-fill {
  height: 100%;
  background: linear-gradient(
    90deg,
    var(--primary) 0%,
    var(--primary-dark) 100%
  );
  transition: width 1s ease;
}

.skill-level {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--primary);
  min-width: 50px;
  text-align: right;
}

.results-actions {
  display: flex;
  justify-content: center;
  gap: var(--spacing-md);
}

.info-box {
  background: var(--gray-50);
  padding: var(--spacing-lg);
  border-radius: var(--radius-lg);
}

.info-box h3 {
  margin-bottom: var(--spacing-sm);
}

.info-box ul {
  list-style-position: inside;
  color: var(--gray-700);
}

/* Animations */
@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes correctPulse {
  0%,
  100% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.1);
    background: var(--success);
    color: white;
  }
}

@keyframes incorrectShake {
  0%,
  100% {
    transform: translateX(0);
  }
  25% {
    transform: translateX(-5px);
    background: var(--error);
    color: white;
  }
  75% {
    transform: translateX(5px);
    background: var(--error);
    color: white;
  }
}

@keyframes badgeAppear {
  from {
    opacity: 0;
    transform: scale(0) rotate(-180deg);
  }
  to {
    opacity: 1;
    transform: scale(1) rotate(0deg);
  }
}

/* Responsive */
@media (max-width: 768px) {
  .screen {
    padding: var(--spacing-sm);
  }

  .container {
    padding: var(--spacing-md);
  }

  .difficulty-buttons {
    grid-template-columns: 1fr;
  }

  .action-buttons {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }

  .number-pad {
    gap: 0.25rem;
  }
}

@media (max-width: 480px) {
  h1 {
    font-size: 1.8rem;
  }

  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Accessibility */
button:focus-visible {
  outline: 3px solid var(--primary);
  outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}

@media (prefers-contrast: high) {
  :root {
    --primary: #0d47a1;
    --gray-700: #000000;
  }
}